A change in JP Morgan’s definition of market risk-related gains and losses has thrown a wrench in what would have been a year without a single day of trading losses under the previous system.

JP Morgan posted a loss on 83 of 260 trading days last year, according to the bank's 10K filing with the Securities and Exchange Commission this week. The bank made gains on 177 days and there was one day – the first of the year – when gains topped $125 million. There were six days when gains topped $75 million. It lost more than $25 million on 12 days.

However, the bank said that it would have been able to report a year without a single day of trading losses but for a change to the way it defined market risk-related gains and losses.

According the annual filing, JP Morgan switched its definition in the fourth quarter of last year “to be consistent with the definition used by the banking regulators under Basel 2.5”.

Those regulations require banks to hold more capital against their market risks, and the a spokeswoman for JP Morgan said the move had been a voluntary one.

The new definition for market risk-related gains and losses include profits and losses on the bank’s risk management positions, but exclude a number of factors including fees, commissions, net interest income, gains and losses from intraday trading and fair value adjustments.

The previous definition took into account a number of factors such as principal transactions revenue for the corporate and investment bank, treasury and chief investment office units and CIB brokerage commissions, underwriting fees and other revenue.

In its third quarter filing with the SEC in November, when the bank was still using its old definition, JP Morgan revealed no loss-making trading days in the nine months to September 31 and three days during the period when gains exceeded $200 million.

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Under the previous system in 2012, the bank posted gains on 220 of 261 days, with gains topping $200 million on eight days.

The change is the latest in the way the bank presents information to investors. In its fourth quarter earnings, JP Morgan for the first time used a funding valuation adjustment, or FVA, for over-the-counter derivatives and structured notes.

--Write to skrouse@efinancialnews.com or follow on Twitter at @bysarahkrouse